Data communications units, designated as hand-held units, are already in wide use, and actually in the form of easily handled units, especially also operable while being held in the hand for decentralized, digital data acquisition and for data transmission between mostly several sources of data and a central data processing installation. They are also in a limited task-oriented extent also used for data processing on the spot and for control by the user.
In the simplest case, data cassettes are used for the data transmission involved. In a higher development stage, a numerical and instruction keyboard, a display, means or use of a barcode hand-held reader as well as suitable print-out devices can be provided; this means that such equipment is conceived as mini-computers provided with suitable interfaces and a rechargeable current supply.
A preferred application area for such hand-held units is a commercial vehicle or a motor vehicle fleet, where vehicle operational and travel data are to be acquired for immediate decisions, for instance maintenance measures, as well as for later tour planning as where the drivers are optimally guided or at least informed by tour plans prepared in a stationary data processing installation.
Indubitably the efficiency of the vehicle use, for instance in commercial freight traffic, can be considerably increased by the application of such a system. A wider application has hitherto however been prevented not by an insufficient acceptance of the electronic data processing system in itself, rather by the units to be handled, part of which were relatively heavy as well as of large volume because of the functions assigned to them.
The shaping of such hand-held units so as to be easily gripped and held in the hand with an appropriate weight distribution and rounding-off of edges is decisive for their acceptance, but also an easily monitored operability and readability of the information to be displayed.
Other criteria are however significant for use in a motor vehicle, namely: a hand-held unit should be mounted in the driver's cab so as to be within easy reach of the driver; it must be attachable so as to be shake-proof; and the attachment or the mounting of the hand-held unit must be adapted to the rough working environment in the motor vehicle. This means that the attachment of the hand-held unit and the contact provisions or the coupling of the hand-held unit with the power and data lines in the vehicle, by means of which the hand-held unit must be connectible with measured value or static transmitters as well as other vehicle instruments or with a vehicle databus, must be performable without any undue care being required or without the user having to look in the direction of this equipment and without being subject to damage.
It can be easily seen that cable and plug-in connections cannot be used in this environment. Furthermore, for hand-held units which have to have a fixed seating on a suitable support, and have to be inserted into guides, for instance into a dovetailed guide, such guides have to be avoided, because with the latter an exact alignment is required in order to avoid tilting. In addition, pocket-shaped or trough-shaped receptacles for hand-held units are unsuitable, since in these cases access is limited.